by Oren Dorell, USA TODAY

by Oren Dorell, USA TODAY

Sanctions relief given to Iran in return for its agreement to suspend part of its nuclear program are not as limited or as reversible as the White House claims, analysts and some lawmakers say.

"They low-balled the value of sanctions relief," says Mark Dubowitz, executive director of the Foundation for Defense of Democracies.

Easing restrictions on Iranian oil sales will "change the market psychology from fear to greed and open up a loophole in the international sanctions regime so big you could drive an oil tanker through," Dubowitz said.

The White House has said Iran will receive "limited, temporary, reversible relief" valued at $7 billion over six months in return for capping some of its uranium enrichment activities that the United States suspects could be aimed at making atomic bombs.

French Foreign Minister Laurent Fabius said Monday that some European sanctions on Iran could be lifted as early as next month.

In selling the deal, President Obama said that if Iran does not meet its commitments then the economic sanctions that are relaxed can be quickly reimposed. But House Majority Leader Eric Cantor said Monday that sanctions cannot be reimposed as quickly as they were eliminated and Iran knows this.

"We have now let the door open to sanctions going away," Cantor told CBS News. "We have said that we will ease up on sanctions which have taken years and years of progress for them to build and to be able to apply the kind of pressure that it did."

It took several years for the United Nations, United States and the European Union to pass and strengthen economic sanctions on Iran to force it to comply with U.N. Security Council resolutions demanding it end all uranium enrichment.

The sanctions froze the international bank assets of individuals and organizations that were suspected of helping Iran obtain nuclear equipment. Imports of Iranian oil were drastically curtailed. European companies were banned from insuring Iranian oil shipments. Embargoes were put in place against trading gold with Iran, buying its vehicles and precious metals.

By the time the Iranians agreed to negotiate for relaxation of the sanctions, the U.N. estimated the sanctions cost Iran $120 million in revenue.

The deal struck Sunday in Geneva will allow countries to buy more Iranian oil, and releases $4.2 billion in cash from oil sales, ends the limits on gold and Iran's auto sector.

"The broader architecture of sanctions will remain in place and we will continue to enforce them vigorously," Obama said. "If Iran does not fully meet its commitments during this six-month phase, we will turn off the relief and ratchet up the pressure."

Most of Iran's economic sectors will remain under sanctions, especially Iran's dominant oil and gas sector. And companies that do enter the Iranian market, even in areas not subject to sanctions, will continue to encounter continuing financial and logistical restrictions, and find it difficult to get paid, said Caitlin Hayden, spokeswoman for Obama's National Security Council.

Some of Obama's allies in the Senate are not impressed and pledged to move ahead with new sanctions legislation to ensure Iran faces sufficient pressure when the interim deal comes to a close.

"This agreement did not proportionately reduce Iran's nuclear program for the relief it is receiving," Sen. Robert Menendez, D-N.J., chairman of the Senate Foreign Relations Committee, said.

The logic of the interim deal is that Iran will get hooked on a reinvigorated economy and decide to give the West more of what it wants on ending its nuclear program, said Aaron David Miller, a former U.S. peace negotiator and adviser to Democratic and Republican secretaries of state.

Iranian "popular pressures will grow as jobs are created, goods become available and the leadership sees the advantage of more and more sanctions relief" â?? and of making more concessions on its nuclear program.

Critics say reimposing the sanctions will be difficult especially for the Europeans who make decisions by consensus.

The United Kingdom, France and Germany may agree but Sweden, Italy and Malta may not, Dubowitz said.

Iran, which has the world's fourth-largest oil reserves, a large auto sector and a population of 80 million people that is 44% under age 25, is an attractive market.

"It's been incredibly difficult to get all members of the E.U. to get on board to implement the sanctions in the first place," he said. "If six months from now there's not a real deal and they want to reinstitute the sanctions, but the Swedes balk, the sanctions will never get reactivated."

Dubowitz says the Obama administration's estimate of the value of sanctions relief fails to count the value of increased confidence in the Iranian economy. And by lifting the auto sector sanctions, the deal rescued the country's second-largest employer, Dubowitz said.

"They gave tens of billions of dollars to Iran in a way that will be excruciatingly difficult to reverse if Iran doesn't comply with the deal or sign a final agreement," Dubowitz said.

The international sanctions limited Iran's ability to operate in international financial markets, cutting its oil revenue by $80 billion since the beginning of 2012, according to the White House. But now that market psychology will work in Iran's favor, says Danielle Pletka, vice president for foreign and defense policy studies at the American Enterprise Institute.

"Once you start to open sanctions even minimally it's a hole in the dike," Pletka said. "We are already seeing Asian businessmen, Chinese in particular, traveling to Iran to make a deal."

But David Cohen, the U.S. Treasury Department's undersecretary for terrorism and intelligence, told Bloomberg News that the U.S. business community should not think Iran is now open for business. Many sanctions remain and will be enforced, he warned.